Transfer‐Based Thin‐Section‐Free MALDI Mass Spectrometry Imaging Using a Platinum‐Coated Porous Plate Formed of Glass Beads

Matrix‐ and surface‐assisted laser desorption/ionization mass spectrometry imaging (MALDI‐ and SALDI‐MSI) are widely used for visualizing molecular distributions not only in medical and pharmaceutical applications but also in plant and food analysis. To overcome limitations associated with sample hardness or fragility, a transfer‐based approach was recently developed as an alternative to thin sectioning. In particular, Pt‐coated porous plates formed of glass beads (transfer plates) have been introduced as robust substrates for thin‐section‐free SALDI‐MSI. In this study, we demonstrate for the first time that these transfer plates also support thin‐section‐free MALDI‐MSI by transferring the entire strawberry cross‐section onto the plate. First, SALDI‐MSI was performed; then, a matrix was applied to the same sample on the transfer plate, which was followed by MALDI‐MSI. Sequential imaging using both modalities enabled comparison under identical conditions. Ion images of hexose, citric acid, and sucrose obtained using both modalities showed qualitative agreement, indicating that the prior SALDI‐MSI and the delocalization caused by subsequent matrix spraying had no substantial effect on the MALDI‐MSI results while using a 200‐μm step size. In addition, anthocyanins localized to the strawberry skin, which could not be detected by SALDI‐MSI, were successfully visualized by MALDI‐MSI, thereby validating the method. These results confirm that MALDI‐MSI can be performed on transfer plates without sectioning, expanding the utility of this sampling platform. The proposed approach utilizing a transfer plate enables efficient acquisition of both SALDI and MALDI data, which is particularly useful when conventional sectioning or sample duplication is impractical.